How does the "output buffer size" affect?

Hi John,

Using sigma for sharc(the application of 2.0,0,and sigma for sharc in sigma of version 2.1.0) for a while,I have changed my buffersize as 128.And yesterday,I have changed one of my schematic in sigma's buffer size to 128 from 64,and the project can be downloaded and running well,but nothing sound from my output.What I can find the difference between this schematic and my former schematic of 128 buffersize is the "output buffer size" after clicking the "Set output buffer size" in the sigma schematic as shown below.

So I just want to know what is the function of "output buffer size"?

Best Regards,

Liang